Open only one popup window (panel)

So i have this function onDisplayError which is called each time if request fails. This means if user press save button and 3 request are failing i currently getting 3 popup messages. My goal is that this function checks if my popup window is already opened. If it is then i will append errors in my already opened window otherwise it should open this error popup

The problem is that i'm still getting multiple popups displayed. I think that the problem is that var errorPanel loses reference so it can't check if this popup (panel) is already opened. How to achieve desired effect? I'm working with extjs 6. If you need any additional information's please let me know and i will provide.

The panel's initComponent function should initialize an empty window, and appendError should contain your logic to append an error (which may be the first error as well as the second or the third) to the list of errors in the panel.